Use of Algae Reactors to
Remediate Eutrophication
in the Mississippi River Delta
Brendan Scott
Joseph Vassios
BZ 572
November 9, 2010
Mississippi River Basin
1.5 Million Square Miles
Ecology of Hypoxia
Introduction – Mississippi River
 Increased fertilization and leaching of top soil
has increased nitrogen concentrations in the
Mississippi River and consequently the Gulf of
Mexico
 Increased concentrations of nitrogen has led to
seasonal eutrophication of the Gulf of Mexico
Nitrogen
 Nitrogen is used by plants for:
 Nucleic acid (DNA & RNA)
 Amino acids
 Pigments
 Eutrophication as a result of increased
nitrogen can lead to:
 Detrimental algae blooms
 Reduced dissolved oxygen (hypoxia)
 Fish kills
http://toxipedia.org/display/toxipedia/Algal+Bloom
Nitrogen’s Role in Eutrophication
http://www.physicalgeography.net/fundamentals/9s.html
Current Regulation of Nitrogen
 EPA limits for nitrogen in drinking water:
 Nitrate – 10 ppm
 Nitrite – 1 ppm
 Ammonia – Varies
 Total N – 11 ppm
 Leaching from agricultural soils is currently unregulated
USGS, 2010
Nitrogen Levels Directly Proportional to Amount of Tile
Farming
USGS, 2010
Current Remediation Strategies
 Current strategies incorporate mitigation by
altering farming processes
 Reduce nitrogen inputs
 Crop rotation
 Modified cultural practices
 Previous research using algae for wastewater
remediation (phytoaccumulation):
 Algae turf scrubber
 Algae biofilm
Algae Turf Scrubber
Algae Biofilm
Qun et al., 2008
Algae Biofilm
Qun et al., 2008
Potential Algae Species
Anabaena cylindrica
Spirogyra sp.
http://plantphys.info/plant_biology/labaids/cyan
obacteriaslides.shtml
http://www.uwsp.edu/biology/courses/botlab/La
b20a.htm
Algae is also intentionally cultivated, supporting a
multimillion dollar international industry
Design Criteria For Algae Reactor
 Simple
 Passive
 Relatively efficient
 Movable
 Exploit a natural ecosystem
 Turn a waste stream into energy
Palate sized for ease of transport with a footprint of 11
square feet
Ergonomically accessible for reach
with a height of 5 feet
Effective surface area of 1320 square feet created by
120 trays spaced one ½ inch apart
Cheap durable construction
materials
Plexi glass for reactor housing
Removable screens as scaffolding
for algae
Hybridization of Existing
Technologies
Wastewater Treatment
Calculations
Monod Growth Kinetics
With variables of
Influent Nitrogen Concentration
Reactor Effluent Substrate Concentration
Specific Growth Rate
Hydraulic Retention Time
S=K[(1+bθ)/(θ(Yq-b)-1)]
Yielded reactor surface areas smaller than
“Dead Zone”
Optimal Residence Time of 8
Days
Calculation Based on Equal
Areas
Area of “Dead Zone”
8000 square miles at peak
Effective surface area of reactor
1320 Square feet
Number of units required for total removal
169 million,
Equivalent to 67 square miles of reactors
0.004% of farm land in Mississippi River basin
Moving Forward
 Create working prototype
 Trials with various algae species, light conditions,
residence times
 Test influent and effluent conditions over long
time span
 Test reactor algae as fertilizer or product stream
 Determine economic viability of reactors
 Conduct risk assessment and feasibility studies
Questions?
References
 Size-Dependent Nitrogen Uptake in Micro and Macroalgae, M.
Hein, Marine Ecology Press Series Vol. 118, 1995
 Sources and Transportation of Nitrogen in the Mississippi River
Basin, D. Goolsby, USGS
 Phytoremediation as a Management Option for Contaminated
Sediments in Tidal Marshes, V. Bert, Environmental Science Vol.
16, 2009
 Nutrient Uptake in Streams Draining Agricultural Catchments of
the Midwestern United States, M. Bernot, Fresh Water Biology
Vol. 51, 2006
 Nutrient Removal Potential of Selected Aquatic Macrophytes,
K. Reddy, Journal of Environmental Quality Vol. 14, 1985
 Nitrogen and Phosphorus Removal from Urban Wastewater by
the Microalga Scendesmus obliquus, M. Martinez, Bioresource
Technology, Vol. 73, 2000
 Nitrogen and Phosphorus in the Upper Mississippi
River: Transport, Processing, and effects on the
river ecosystem, J. Houser, Hydrobilogia Vol. 640,
2010
 Nutrient Content of Seagrass and Epiphytes in
the Northern Gulf of Mexico: Evidence of
Phosphorus and Nitrogen Limitation, M. Johnson,
Aquatic Botany Vol. 85, 2006
 Reducing Hypoxia in the Gulf of Mexico: Advise
from Three Models, D. Scavia, Estuaries Vol. 27,
2004
 Limnology, Third Edition, R. Wetzel, Academic
Press
 Ecological Stoichiometery in Freshwater Benthic
Systems: Recent Progress and Perspectives, W. Cross,
Freshwater Biology Vol. 50, 2009
 Postaudit of Upper Mississippi River BOD/DO Model,
W. Lung, ASCE
 Environmental Biotechnology: Principals and
Applications, P. McCarty, McGraw-Hill, 2001
 An economic assessment of algal turf scrubber
technology for treatment of dairy manure effluent, C.
Pizarro, Biological Engineering Vol. 26, pg. 321-326,
2006
 Removing nitrogen and phosphorus from simulated
wastewater using algal biofilm technique, W.E.I. Qun,
Front. Environ. Sci. Engin. Vol. 2, pg. 446-451, 2008
 Nutrients in the Nation’s Streams and Groundwater,
1992-2004, Circular 1350, N. Dubrovsky, USGS, 2010.
Accessed at: http://pubs.usgs.gov/circ/1350/